Do not use bleach, as the plastic that absorbs the yellow stain from the carrots may also absorb the bleach smell and taste.

If the baking soda doesn't work, try lemon juice or vinegar, as they are acids and so the opposite of baking soda. you may want to let the bowl soak with baking soda and water overnight. If this is Tupperware or something like that, you might scratch the surface with a baking soda scrub.

I run all my microwavable plastic things through the dishwasher. This takes out most stains, and I just ignore the ones that it doesn't! If you can't wash it in the dishwasher, you likely shouldn't be using it in the microwave either.